I have got a few capacitors in my sortiment which have got dash-dot markings above and below the value code, like this:


What do these dash-dot codes mean? Do they reflect voltage rating or temperature dependency, or do they just denote a production date/lot?

  • 2
    \$\begingroup\$ I thought I knew almost everything about capacitors and their markings, but this is new. Can you tell us what brand they are? \$\endgroup\$ Jun 16, 2016 at 3:52
  • \$\begingroup\$ @RobertEndl, unfortunately I have no clue; I was hoping the colour of the housing hints at the brand, but I could not find anything meaningful so far... \$\endgroup\$
    – aschipfl
    Jun 16, 2016 at 7:15
  • \$\begingroup\$ My guess is a date code. It must be brand specific, I've never seen anything like it. China has a huge number of factories that make similar parts, but they often have a "type code" that tells you the kind of film capacitor it is (polyester, film/foil etc). Sometimes the old German code is used and sometimes the newer Chinese code. The color is typical of any number of Chinese companies. \$\endgroup\$ Jun 16, 2016 at 8:32
  • \$\begingroup\$ @RobertEndl, after some image searching throughout the web, I think the capacitors are of PET type manufactured by Panasonic (these look quite similar: 6224634 and 6224779) -- does this help? I guess I will contact Panasonic the next days and provide an answer here as soon as they reply... \$\endgroup\$
    – aschipfl
    Jun 16, 2016 at 10:29
  • \$\begingroup\$ Sure enough, I found some (not all) Panasonic parts with such dots. Let us know what Panasonic says. \$\endgroup\$ Jun 16, 2016 at 16:02

3 Answers 3


After having found out that the capacitors at hand were manufactured by Panasonic (by searching the web for similar capacitor images; for instance, these capacitors look quite similar: 6224634 and 6224779), I contacted them and asked for the meaning of the dash-dot markings. This is what they replied basically:

  • there are two lines of text; the first one identifies value by three decimal figures (2 significant digits, 1 multiplier (power of 10 Picofarads)) and tolerance (acc. to JIS);
  • the second line of text identifies the rated voltage value in volts and the year of production by a single letter;
  • the dots below the second line of text identify the month of production;
  • the dashes above the year marking identify the production facility;

This does not perfectly suit the capacitors I showed in the question (as they might be quite old), but it perfectly meshes the example capacitors I linked herein above.
So I assume Panasonic revised the dash-dot marking meanwhile. As soon as they replied to my follow-up question, I will update this answer accordingly.

  • 1
    \$\begingroup\$ Thanks for the update. My answer appears to be wrong in this case. I'll let it stand as it might be relevant for some other devices. \$\endgroup\$
    – Transistor
    Jun 20, 2016 at 17:15

They may be a "lane marker" for the equipment producing the components. There are many industrial processes which can benefit from being able to identify which machine, mould cavity or lane in a multi-lane machine produced the part.

Typically, for components such as these, sample parts will be tested off-line to measure tolerance, etc., and the lane marker would help narrow down the fault to one particular section of the process. In the event of scrapping out-of-spec parts the rejection can be reduced to the problem lane thereby saving money.


Specifically for Panasonic film capacitors, which these appear to be, take a look at https://industrial.panasonic.com/ww/products-cap/film-capacitors/specification.

The documents, specifically the 'Product Drawings' for each of the types, can go far with respect to identifying the capacitor. As mentioned by others, the letter beside the voltage rating, along with the dots and dashes indicate the date code but the position of the letter is also indicative of the capacitor type. For example, looking at the produce drawing of one of the 250V ECQE(F) capacitors shows the date code on the right side of the voltage value (https://industrial.panasonic.com/content/data/CP/PDF/qef2_f_e.pdf) where the product drawing of a 250V ECQE(B) shows the date code on the left side of the voltage code (https://industrial.panasonic.com/content/data/CP/PDF/qeb2_b_e.pdf)


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